Mobbs excelled as an all-round sportsman at Bedford Modern School before continuing his rugby career with Northampton where he was soon made captain. He played for the East Midlands and the Barbarians before winning his first England cap against the original Australian tourists in 1909. At the outbreak of the First World War he tried to enlist but was reportedly turned down for being too old. Not to be deterred he issued rallying call to his friends and associates and pulled together a group of 250 men who would join the Northamptonshire regiment and become known as Mobbs' Own. He rose to the rank of Lietenant Colonel before he was killed in battle on July 31, 1917 at Zillebeke during the Third Battle of Ypres. His body has never been found and his name adorns the Menin Gate memorial. In 1921 the first Mobb's Memorial Match was held between the East Midlands and the Barbarians at Franklin's Gardens and has continued ever since.